Core box blow hole liner

ABSTRACT

HOLE STOOL SIMULTANEOUSLY WITH REMOVAL OF THE FINISHED CORE FROM THE CORE BOX. A LINER FOR THE BLOW HOLE OF A SAND CORE BOX IN THE FORM OF A WAX-IMPREGNATED OR COATED PAPER TUBE WHEREIN THE WAX ACTS AS A RELEASE AGENT AS IT MELTS DURING THE CORE-MAKING OPERATION TO FACILITATE STRIPPING OF THE BLOW

, 1971 D. H. PIKEY CORE BOX BLOW HOLE LINER Filed July 29, 1969 United States Patent 3,614,979 CORE BOX BLOW HOLE LINER Donald H. Pikey, Chicago, 111., assignor to International Harvester Company, Chicago, Ill. Filed July 29, 1969, Ser. No. 845,805 lint. Cl. B22c /24 US. Cl. 164-228 6 Claims ABSTRACT OF THE DISCLOSURE A liner for the blow hole of a sand core box in the form of a wax-impregnated or coated paper tube wherein the wax acts as a release agent as it melts during the core-making operation to facilitate stripping of the blow hole stool simultaneously with removal of the finished core from the core box.

This invention relates to a core box blow hole liner and more particularly to a liner in the form of a waximpregnated or coated paper tube positionable within a blow hole or sand entrance passageway of a core box whereby the wax on the outside of or contained within the liner acts as a release agent when it melts during the sand baking or hardening step of the core-making process to facilitate stripping of the blow hole stool simultaneously with the removal of the finished core from the core box.

Two well known processes for the formation of sand cores for utilization in the founding of metal castings are identified as the hot core box method and the oilsand core blower method. In essence, both methods involve the filling of a core box cavity with core sand to form cores of various shapes. The core sand charge, in loose or granular form, is introduced into the core box cavity through an entrance passageway formed through a wall of the core box which entrance passageway is commonly referred to as a blow hole. The core sand is carried into the core box cavity by means of a compressed air stream developed by a core blower. The core box is pre-heated to a predetermined temperature prior to the introduction of the core sand therein when the hot core box method is practiced and is heated to a predetermined temperature after the core sand is introduced into the core box cavity when the oil-sand core blowing method is utilized. In both methods, the heat imparted to the core sand contained within the core box causes it to harden. Once the core sand forming the core is properly cured and hardened, it is necessary to remove or strip the finished core from the core box. Inasmuch as the blow hole is completely filled with granular core sand concurrently with the core box cavity during the core box cavity filling operation, a hardened blow hole stool heretofore remained in the blow hole after the finished core was stripped from the core box. The hardened blow stool would then have to be chipped out with a hard wooden plug or soft metal rod. Obviously, such blow hole stool removing operation added to the cost and complexity of producing sand cores.

Attempts to coat the surface defining the blow hole with grease or some other release agent prior to the introduction of the core sand into the core box cavity in order to prevent sticking of the blow hole stool to the core box wall surface defining the blow hole were unsuccessful. Failure of the release agent applied to the blow hole wall to prevent sticking of the blow hole stool was partly due to the high velocity air-sand stream which had the effect of shearing off such release agent coating during the core box cavity filling operation. It has also been established that because of the extremely high velocity of the air-sand blow or stream, resin is actually 3,614,979 Patented Oct. 26, 1971 sheared from the sand grains and forms a glue-like substance on the wall of the blow hole to counteract the function of the release agent.

As pointed out hereinbefore, a primary objective of the present invention is to provide a tubular liner for the blow hole of a sand core box in the form of a wax-impregnated or coated paper tube wherein the wax acts as a release agent as it melts during the core-making operation. Thus, after the core is hardened and cured, the blow hole stool is readily stripped from the core box simultaneously with the finished core. The tubing or liner with the hardened blow hole stool therein becomes a part of the core as the core is removed from the core box and once the core is removed from the core box the liner containing the blow hole stool is merely broken off and removed from the finished core.

A further object is to provide a blow hole liner in the form of wax paper tubing, such as a soda straw, which is adapted to be fitted snugly within the blow hole or entrance passageway of a sand core box before the core box cavity is filled with granular core sand and whereby the heat imparted to the core box during the core making operation causes the wax of the liner to melt and act as a release agent between the liner and the blow hole wall to facilitate stripping or removing of the liner and the blow hole stool within the liner from the core box after the finished core is properly cured.

A still further object is to provide relatively inexpensive means for preventing the blow hole stool from sticking to the wall of the blow hole and to facilitate removal therefrom after setting of the core.

The foregoing and other important objects and desirable features inherent in and encompassed by the invention, together with many purposes and uses, thereof will become readily apparent from reading of the ensuing description in conjunction with annexed drawings, in which:

FIG. 1 is a perspective view, partly broken away and in section, of core making equipment embodying the invention;

FIG. 2 is a perspective view of a core box of the type illustrated in FIG. 1 with the blow hole and core cavity indicated in dotted lines; the equipment is shown prior to the insertion of a blow hole liner in operative position;

FIG. 3 is an exploded view in perspective of one-half of the core box shown in FIG. 2 after hardening or curing of the sand core;

FIG. 4 is a vertical sectional view taken substantially along line 44 of FIG. 2; and

FIG. 5 is an enlarged detail view in perspective of a portion of a blow hole liner or sleeve forming a part of the invention.

Referring to the drawings in detail, wherein like reference characters represent like elements throughout the various views, the present embodiment of the invention is schematically illustrated in relation to equipment utilized to make sand cores by either of the aforementioned lwell-known methods. The core-making equipment in cludes a core box 11 which comprises two opposed cornplementary sections 12, 13, with corresponding cutaway portions together forming a core cavity 14 and a generally cylindrical blow hole 15 communicating therewith. Preferably, projecting pins 16 are suitably mounted in the semi-cylindrical side walls 15a, 15b of blow hole 15 to support a liner or sleeve 17 receivable in snugly fitting relation with the blow hole -15 and with its innermost extremity closely adjacent the surface of the core box 12 defining the upper part of the cavity 14, and its outermost extremity co-terminous with hole 15.

The core box 11 being in operative position in relation to a sand magazine 20, as shown in FIG. 1, of a conventional core blowing machine with the blow hole 15 in operative communication with the outlet 21 of the blow plate 22 of a blow head 23, upon air being introduced into magazine 20 through conduit 24, the fiow of air and sand will take the course generally of the arrows, issuing through outlet 21 into lined blow hole 15, thence to core box cavity 14 to form core 18 (schematically indicated in simple form).

As pointed out hereinbefore, pre-coating of the blow hole 15 with a release prior to the introduction of the core-sand mixture to the core cavity 14 presented quite a few operational difficulties and problems. It was also pointed out that because of the extremely high velocity of the blow, not only would the release agent coating be sheared from the sides of the blow hole rending it effectual but also the resin was sheared from the sand grains to thus form a glue-like substance which enhanced adhesion of the core sand within the blow hole to the wall surface defining the blow hole. Consequently, prior to the present invention, the blow stool would firmly adhere to the side walls 15a, 15b of the blow hole 15 after the core curing operation and would have to be tediously chipped out with a hard wooden plug or soft metal rod. Obviously, such blow stool removing operation contributed considerably to the overall production time and cost for making a core. In order to obviate the problem of removing the blow stool from the core box "11 after curing of the core, a liner or sleeve 17 is utilized in the present invention. To this end, it has been found most efficacious to utilize waxen material in the manufacture of the sleeve 17 which material is capable of withstanding applied heat of operation in a temperature range of 350 to 600 F. for a period of from 5 to seconds depending on the working conditions of a given project. An inexpensive example of a sleeve manufactured in this manner is a common soda straw which is commercially readily available. The manufacture of a common soda straw usually involves dipping a suitable paper tube in molten paraflin wax. The wax content of such a liner 17 has a lubricating quality when the liner is heated during the core-making operation preventing adhesion of the liner 17 and, hence, the sand enclosed by the liner 17 within the blow hole 15, to the walls a, 15b of the blow hole 15. Thus, when the finished or cured core 18 is removed from the core box sections 12 and 13 the core box spool in the form of an appendage will be readily removed intact concurrently therewith. Thereafter, the appendage 25 may be easily broken off from the core 18 without injuring such core 18.

From the foregoing, it will be appreciated that the wax on the outside of the liner or sleeve 17 acts as a release agent as it melts and, after the core 18 is set, the appendage 25 formed by the liner 17 and the baked core-sand mixture contained therein will strip completely and easily out of the core box 11 along with the core 1 8. Accordingly, it will be appreciated that the present invention decreases tremendously the production time for and expense of making cores.

What is claimed is:

1. A molding assembly for making sand cores comprising:

a core box of the type adapted to be subjected to heat during the core-making operation, said core box having a core-forming cavity therein, and a generally 4 cylindrical blow hole extending through the wall of said core box having one end opening into said cavity and its opposite end capable of being placed in communication with a source of core sand under air pressure so as to enable said cavity and blow hole to be filled with core sand; and

substantially tubular release agent means disposed within said blow hole and being responsive to heating of said core box during the core-making operation for providing a layer of lubricant between substantially the entire wall portion of said core box defining said blow hole and the core sand contained within such wall portion whereby said core sand received in said blow hole during the core-making operation may be readily removed from the core box simultaneously with the finished core.

2. A molding assembly for making sand cores as set forth in claim 1, wherein said release agent means includes a liner supported in said blow hole, said liner including a substantially solid material responsive to the application of heat thereto to become liquid so as to provide said lubricant layer and prevent adhesion of said liner to said wall portion defining said blow hole.

3. A molding assembly for making sand cores as set forth in claim 2, wherein said liner separates the core sand contained within said wall portion defining said blow hole and said wall portion, said liner being supported in abutting engagement with said wall portion and being generally co-extensive longitudinally with said blow hole.

4. A molding assembly for making sand cores as set forth in claim 1, wherein said release agent means includes a liner removably supported in abutting relation with said wall portion and being generally co-extensive longitudinally with said blow hole, said liner comprising a waxed paper tube affording a lubricant layer between the outer surface thereof and said wall portion when said core box is subjected to heat during the core-making operation to thereby prevent adhesion of said liner to said wall portion defining said blow hole.

5. A molding assembly for making sand cores as set forth in claim 4, wherein said waxed paper tube is further characterized as coalescing with the core sand received in said blow hole during the core-making operation, said coalescence of said waxed paper tube and such core sand effects the formation on the finished core of a disposable appendage freely removable from said core box simultaneously with the finished core.

6. A molding assembly for making sand cores as set forth in claim 5, wherein said waxed paper tube is further characterized as being able to withstand heat in the temperature range of 350 to 600 F. for from five to ten seconds.

References Cited UNITED STATES PATENTS 1,751,470 3/1930 Brown 164229 3,243,397 3/1966 Herkimer 164-72 3,401,735 9/1968 Pursall 249ll5 X 3,443,627 5/1969 Watts 16445 3,520,349 7/1970 Watts 16434 J. SPENCER OVERHOLSER, Primary Examiner J. S. BROWN, Assistant Examiner 

